1st-2nd shift at WOT & backfire

[Jack Clements]

I have a 1998 chevy suburban 4x4, 5.7 vortec, 4l60e with about 150k. Ever since I got the truck with 148k it has never shifted from 1st to 2nd at WOT. As well as it not shifting when on the floor it gets up to about 3500, stays there and backfires and pops. Its kind of like it hits a rev limiter. When not on the floor the truck runs flawlessy and when it park it will run up to 5k with no problem. It doesnt seem as if the trans is slipping because it will not get past 3500 its like something is holding the motor back. Any help will be greatly appreciated. Thank you!

 

[Dirty98]

I have a similar problem with my 4.3 4l60e except it stays at 5k WOT in first. do you have a rough idle? couple people told me it might be the TPS. curious to see what fixes yours

 

[Supercharged111]

TPS will cause shifting issues but should not prevent the motor from revving up regardless of load.

 

[obxjake]

I have a 1998 chevy suburban 4x4, 5.7 vortec, 4l60e with about 150k. Ever since I got the truck with 148k it has never shifted from 1st to 2nd at WOT. As well as it not shifting when on the floor it gets up to about 3500, stays there and backfires and pops. Its kind of like it hits a rev limiter. When not on the floor the truck runs flawlessy and when it park it will run up to 5k with no problem. It doesnt seem as if the trans is slipping because it will not get past 3500 its like something is holding the motor back. Any help will be greatly appreciated. Thank you!

Shift sensors...take to GM dealer who can read the codes and replace. Same on mine...works perfect now.

 

[Supercharged111]

Shift sensors...take to GM dealer who can read the codes and replace. Same on mine...works perfect now.

There is no such thing as a shift sensor. A shift solenoid on the other hand could cause a shifting issue, but it should be throwing a code for that. I've had shift solenoid issues before and they don't prevent an engine from rapping out nor do they induce a backfire.